Described herein is a printing device, more particularly an ink jet printing device, capable of forming images on a substrate in either or both of a regular height and a raised height of print on the substrate. Also described is a method of forming images with the printing device. The printing device herein provides for a low cost means enabling printing in raised height format, for example for Braille and raised graph applications, when required.
U.S. Pat. No. 6,644,763 describes a method for creating raised and special printing effects using ink jet technology. The method includes the steps of depositing a light curable photo-polymer material (18) on the area selected for the printing effects, and curing the area. The amount of material to be deposited corresponds to the area selected for the printing effects and the height of the raised area relative to the medium (22) on which the photo-polymer material (18) is deposited. See the Abstract.
U.S. Pat. No. 5,627,578 describes a method and device for raised letter or graphics printing, by means of a sprayed wet ink deposition on a print substrate. Subsequent dispensing of thermographic powder thereon, with adherence of the powder only to the wet ink, followed by heating to a fixing temperature of the powder, results in the raised lettering or graphics. A standard portable ink jet printer of the bubble jet type, controlled, with graphics software control, by a personal computer, provides the requisite non-contacting ink deposition. The dispensing cartridges of the ink jet printer are provided with non-contact-drying ink formulations (with two or more separate colors, if desired) for the portion of graphics or printing which is to be in raised form. A thermographic powder dispenser and heating member is connected to the output of the ink jet printer, or integrated therewith for completion of the raised printing process. Raised and non-raised printing is also possible by use of separately dispensed drying and non-drying inks. See the Abstract.
Ink jet printing devices are known in the art. For example, ink jet printing devices are generally of two types: continuous stream and drop-on-demand. In continuous stream ink jet systems, ink is emitted in a continuous stream under pressure through at least one orifice or nozzle. The stream is perturbed, causing it to break up into droplets at a fixed distance from the orifice. At the break-up point, the droplets are charged in accordance with digital data signals and passed through an electrostatic field that adjusts the trajectory of each droplet in order to direct it to a gutter for recirculation or a specific location on a recording medium. In drop-on-demand systems, a droplet is expelled from an orifice directly to a position on a recording medium in accordance with digital data signals. A droplet is not formed or expelled unless it is to be placed on the recording medium. There are generally three types of drop-on-demand ink jet systems. One type of drop-on-demand system is a piezoelectric device that has as its major components an ink filled channel or passageway having a nozzle on one end and a piezoelectric transducer near the other end to produce pressure pulses. Another type of drop-on-demand system is known as acoustic ink printing. As is known, an acoustic beam exerts a radiation pressure against objects upon which it impinges. Thus, when an acoustic beam impinges on a free surface (that is, liquid/air interface) of a pool of liquid from beneath, the radiation pressure which it exerts against the surface of the pool may reach a sufficiently high level to release individual droplets of liquid from the pool, despite the restraining force of surface tension. Focusing the beam on or near the surface of the pool intensifies the radiation pressure it exerts for a given amount of input power. Still another type of drop-on-demand system is known as thermal ink jet, or bubble jet, and produces high velocity droplets. The major components of this type of drop-on-demand system are an ink filled channel having a nozzle on one end and a heat generating resistor near the nozzle. Printing signals representing digital information originate an electric current pulse in a resistive layer within each ink passageway near the orifice or nozzle, causing the ink vehicle (usually water) in the immediate vicinity to vaporize almost instantaneously and create a bubble. The ink at the orifice is forced out as a propelled droplet as the bubble expands.
In a typical design of a piezoelectric ink jet device, the image is applied by jetting appropriately colored inks during four to eighteen rotations (incremental movements) of a substrate, such as an image receiving member or intermediate transfer member, with respect to the ink jetting head. That is, there is a small translation of the print head with respect to the substrate in between each rotation. This approach simplifies the print head design, and the small movements ensure good droplet registration. At the jet operating temperature, droplets of liquid ink are ejected from the printing device. When the ink droplets contact the surface of the recording substrate, they quickly solidify to form a predetermined pattern of solidified ink drops.
Ink jet printing processes may employ inks that are solid at room temperature and liquid at elevated temperatures. Such inks may be referred to as solid inks, hot melt inks, phase change inks and the like. For example, U.S. Pat. No. 4,490,731, the disclosure of which is totally incorporated herein by reference, discloses an apparatus for dispensing solid ink for printing on a substrate such as paper. In thermal ink jet printing processes employing hot melt inks, the solid ink is melted by the heater in the printing apparatus and utilized (jetted) as a liquid in a manner similar to that of conventional thermal ink jet printing. Upon contact with the printing substrate, the molten ink solidifies rapidly, enabling the colorant to substantially remain on the surface of the substrate instead of being carried into the substrate (for example, paper) by capillary action, thereby enabling higher print density than is generally obtained with liquid inks. Advantages of a phase change ink in ink jet printing are thus elimination of potential spillage of the ink during handling, a wide range of print density and quality, minimal paper cockle or distortion, and enablement of indefinite periods of nonprinting without the danger of nozzle clogging, even without capping the nozzles.
The use of ink jet printers in forming raised printed images is also known, for example as indicated in U.S. Pat. Nos. 6,644,763 and 5,627,578 above. However, these printers for forming raised images are typically dedicated machines designed and used solely for raised print applications, such as forming Braille images. Where a user requires only a certain portion of print jobs to be done utilizing raised print, it can be costly for the user to have two print devices, one strictly for the raised print jobs.
What is still desired is a cost-effective ink jet printing device that is capable of forming both regular print images and raised print images.